Final answer:
The attribute 'android: show As Action="if Room"' displays the menu item icon on the action bar when there is sufficient space. It's intended to help provide a dynamic and user-friendly interface in Android applications.
Step-by-step explanation:
The menu item attribute that displays the icon for the menu item in the action bar only when there's enough room is B. android: show As Action="if Room". This attribute specifies that the item should appear as an action button when there is space available in the action bar. If there isn't enough room in the action bar, the item will be placed in the overflow menu. The android: show As Action attribute can take multiple values, but the "if Room" value is the one that meets the requirement described.
Option A (always) forces the item to always show, ignoring the space limitations, Option C (never) never shows the item as an action button (it will always be in the overflow menu), and Option D (android: visible="if Room") is not a valid attribute related to this behavior.